diff --git a/src/app/automation.rs b/src/app/automation.rs
index dfd666579..a6e10ddba 100644
--- a/src/app/automation.rs
+++ b/src/app/automation.rs
@@ -700,6 +700,9 @@ impl OpenCADStudio {
         };
         match req["op"].as_str().unwrap_or("") {
             "new" => {
+                if self.tabs[self.active_tab].block_test.is_some() {
+                    return err("Close Test Block before replacing the drawing.");
+                }
                 if self.tabs[self.active_tab].block_edit_history.is_some() {
                     return err("Close the block editor before replacing the drawing.");
                 }
@@ -726,6 +729,9 @@ impl OpenCADStudio {
             }
             #[cfg(not(target_arch = "wasm32"))]
             "open" => {
+                if self.tabs[self.active_tab].block_test.is_some() {
+                    return err("Close Test Block before replacing the drawing.");
+                }
                 if self.tabs[self.active_tab].block_edit_history.is_some() {
                     return err("Close the block editor before replacing the drawing.");
                 }
@@ -792,6 +798,7 @@ impl OpenCADStudio {
                 if self.command_line.error_revision != error_revision {
                     return err(self.command_line.last_error.clone().unwrap_or_default());
                 }
+                let i = self.active_tab;
                 let after = self.tabs[i].scene.document.entities().count();
                 // A command can finish with an interactive surface still open:
                 // the in-place text editor (the `TEXT` content step), the MTEXT
@@ -996,6 +1003,9 @@ impl OpenCADStudio {
                 json!({ "ok": true, "selected": self.tabs[i].scene.selected_entities().len() })
             }
             "save" => {
+                if self.tabs[self.active_tab].block_test.is_some() {
+                    return err("Test Block is temporary and cannot be saved.");
+                }
                 let i = self.active_tab;
                 let path = req["path"]
                     .as_str()
@@ -1533,6 +1543,11 @@ impl OpenCADStudio {
     #[cfg(not(target_arch = "wasm32"))]
     pub(super) fn save_verified_request(&mut self, req: &Value) -> Result<Value, Value> {
         let i = self.active_tab;
+        if self.tabs[i].block_test.is_some() {
+            return Err(
+                json!({"ok":false,"code":"temporary_document","error":"Test Block is temporary and cannot be saved."}),
+            );
+        }
         let Some(raw_path) = req["path"].as_str() else {
             return Err(
                 json!({"ok":false,"status":"failed","code":"path_required","error":"save_verified requires an explicit absolute path"}),
diff --git a/src/app/block_editor.rs b/src/app/block_editor.rs
index 529a4c845..a74bbd65f 100644
--- a/src/app/block_editor.rs
+++ b/src/app/block_editor.rs
@@ -499,6 +499,7 @@ impl OpenCADStudio {
             &session.return_camera,
         );
         self.cancel_attr_editor();
+        self.discard_block_tests(self.tabs[i].id);
     }
 
     pub(super) fn request_block_edit_close(
@@ -506,6 +507,7 @@ impl OpenCADStudio {
         i: usize,
         continuation: BlockEditContinuation,
     ) -> Task<Message> {
+        let id = self.tabs[i].id;
         if self.tabs[i].active_block_edit_session().is_some() {
             if self.block_edit_dirty(i) {
                 self.active_tab = i;
@@ -515,6 +517,7 @@ impl OpenCADStudio {
             }
             self.close_block_edit(i, true);
         }
+        let i = self.tabs.iter().position(|tab| tab.id == id).unwrap();
         self.continue_after_block_edit(continuation, i)
     }
 
@@ -564,6 +567,7 @@ impl OpenCADStudio {
         self.pending_block_close = None;
         self.active_modal = None;
         self.close_block_edit(i, !save);
+        let i = self.tabs.iter().position(|tab| tab.id == id).unwrap();
         self.continue_after_block_edit(continuation, i)
     }
 
@@ -583,7 +587,11 @@ impl OpenCADStudio {
         {
             return self.request_block_edit_close(i, BlockEditContinuation::Quit);
         }
-        if self.tabs.iter().any(|tab| tab.dirty) {
+        if self
+            .tabs
+            .iter()
+            .any(|tab| tab.dirty && tab.block_test.is_none())
+        {
             self.pending_close = Some(super::PendingClose::Quit);
             self.open_unsaved_dialog_window()
         } else {
diff --git a/src/app/block_test.rs b/src/app/block_test.rs
new file mode 100644
index 000000000..729c4d829
--- /dev/null
+++ b/src/app/block_test.rs
@@ -0,0 +1,163 @@
+use super::{document::DocumentTab, Message, OpenCADStudio};
+use codec::entities::{AttributeEntity, Entity, Insert};
+use codec::EntityType;
+use iced::Task;
+
+pub(super) struct BlockTestSession {
+    pub source_id: u64,
+}
+
+impl OpenCADStudio {
+    pub(super) fn refuse_block_test_save(&mut self, i: usize) -> bool {
+        if self.tabs[i].block_test.is_none() {
+            return false;
+        }
+        self.command_line.push_error(
+            crate::t!("Test Block is temporary. Close it and save from the Block Editor.").as_ref(),
+        );
+        true
+    }
+
+    pub(super) fn open_block_test(&mut self, i: usize) -> Task<Message> {
+        let source_id = self.tabs[i]
+            .block_test
+            .as_ref()
+            .map_or(self.tabs[i].id, |test| test.source_id);
+        let Some(i) = self.tabs.iter().position(|tab| tab.id == source_id) else {
+            return Task::none();
+        };
+        let Some(session) = self.tabs[i].active_block_edit_session() else {
+            self.command_line
+                .push_error(crate::t!("No block editor is open.").as_ref());
+            return Task::none();
+        };
+        let name = session.block_name.clone();
+        let definition = session.br_handle;
+        self.finish_pending_history(i);
+        let mut document = self.tabs[i].scene.document.clone();
+        // Keep definitions and their native relationships in the clone. Only
+        // drawing-space contents are replaced by the temporary reference.
+        let spaces: Vec<_> = document
+            .block_records
+            .iter()
+            .filter(|record| record.is_model_space() || record.is_paper_space())
+            .map(|record| record.handle)
+            .collect();
+        let removed: Vec<_> = document
+            .entities()
+            .filter(|entity| {
+                spaces.contains(&entity.common().owner_handle)
+                    && !matches!(entity, EntityType::Block(_) | EntityType::BlockEnd(_))
+            })
+            .map(|entity| entity.common().handle)
+            .collect();
+        for handle in removed {
+            document.remove_entity(handle);
+        }
+        for record in document
+            .block_records
+            .iter_mut()
+            .filter(|record| spaces.contains(&record.handle))
+        {
+            record.entity_handles.retain(|handle| {
+                *handle == record.block_entity_handle || *handle == record.block_end_handle
+            });
+            record.insert_handles.clear();
+            record.insert_count_bytes.clear();
+        }
+        document.header.show_model_space = true;
+        crate::scene::block_visibility::finish_editing(&mut document, definition);
+        let record = document.block_records.get(&name).unwrap();
+        let base = record.base_point;
+        let mut insert = Insert::new(&name, codec::types::Vector3::ZERO);
+        insert.common.layer = self.tabs[i].active_layer.clone();
+        insert.common.handle = document.allocate_handle();
+        insert.common.owner_handle = document.header.model_space_block_handle;
+        let transform = crate::scene::render_graph::insert_transform_with_base(&insert, base);
+        for entity in document.entities_in_block(&name) {
+            if let EntityType::AttributeDefinition(definition) = entity {
+                if !definition.flags.constant {
+                    let mut attribute = AttributeEntity::from_definition(definition, None);
+                    attribute.attdef_handle = definition.common.handle;
+                    attribute.apply_transform(&transform);
+                    insert.attributes.push(attribute);
+                }
+            }
+        }
+        for attribute in &mut insert.attributes {
+            attribute.common.handle = document.allocate_handle();
+            attribute.common.owner_handle = insert.common.handle;
+            if let Some(text) = &mut attribute.embedded_mtext {
+                text.common.handle = document.allocate_handle();
+                text.common.owner_handle = attribute.common.handle;
+                text.common.raw_record = None;
+                text.common.xdictionary_handle = None;
+                text.common.reactors.clear();
+            }
+        }
+        if !insert.attributes.is_empty() {
+            insert.seqend_handle = Some(document.allocate_handle());
+        }
+        if let Err(error) = document.add_entity(EntityType::Insert(insert)) {
+            self.command_line.push_error(&error.to_string());
+            return Task::none();
+        }
+        let mut tab = DocumentTab::new_drawing(0);
+        tab.tab_title = crate::tf!("Test Block Window - {}", name).into_owned();
+        tab.block_test = Some(BlockTestSession { source_id });
+        tab.active_layer = self.tabs[i].active_layer.clone();
+        tab.scene.document = document;
+        tab.scene.named_parameters = self.tabs[i].scene.named_parameters.clone();
+        tab.scene.parametric_constraints = self.tabs[i]
+            .scene
+            .parametric_constraints
+            .iter()
+            .filter(|set| {
+                matches!(
+                    set.scope,
+                    crate::scene::parametric_constraints::ParametricScope::Block(_)
+                )
+            })
+            .cloned()
+            .collect();
+        tab.scene.material_base_dir = self.tabs[i].scene.material_base_dir.clone();
+        tab.scene.sync_annotation_scale_from_header();
+        tab.scene.rebuild_derived_caches();
+        tab.scene.set_current_layout("Model".into());
+        self.discard_block_tests(source_id);
+        self.visibility_popup = None;
+        self.grip_popup = None;
+        self.grip_hover = None;
+        self.tabs.push(tab);
+        self.active_tab = self.tabs.len() - 1;
+        self.sync_ribbon_layers();
+        self.sync_ribbon_styles();
+        self.sync_ribbon_from_selection();
+        self.refresh_block_palette();
+        self.refresh_properties();
+        self.ribbon.set_block_editing(false);
+        self.ribbon.set_block_testing(true);
+        self.dispatch_command("ZOOM EXTENTS")
+    }
+
+    pub(super) fn close_block_test(&mut self, i: usize) -> Task<Message> {
+        if self.tabs[i].block_test.is_none() {
+            self.command_line
+                .push_error(crate::t!("No Test Block is open.").as_ref());
+            return Task::none();
+        }
+        self.on_tab_close(i)
+    }
+
+    pub(super) fn discard_block_tests(&mut self, source_id: u64) {
+        for index in (0..self.tabs.len()).rev() {
+            if self.tabs[index]
+                .block_test
+                .as_ref()
+                .is_some_and(|test| test.source_id == source_id)
+            {
+                let _ = self.on_tab_close(index);
+            }
+        }
+    }
+}
diff --git a/src/app/block_test_tests.rs b/src/app/block_test_tests.rs
new file mode 100644
index 000000000..8fa9a2647
--- /dev/null
+++ b/src/app/block_test_tests.rs
@@ -0,0 +1,346 @@
+use super::{Message, ModalKind, OpenCADStudio};
+use codec::entities::{Insert, Line};
+use codec::types::Vector3;
+use codec::{EntityType, Handle};
+
+fn fixture() -> (OpenCADStudio, usize, Handle) {
+    let mut app = OpenCADStudio::new_for_test();
+    app.automation_op(r#"{"op":"new"}"#);
+    let i = app.active_tab;
+    app.tabs[i].scene.define_block_raw(
+        "SAMPLE",
+        Vector3::new(10.0, 20.0, 0.0),
+        vec![EntityType::Line(Line::from_points(
+            Vector3::new(10.0, 20.0, 0.0),
+            Vector3::new(15.0, 20.0, 0.0),
+        ))],
+    );
+    app.tabs[i]
+        .scene
+        .document
+        .block_records
+        .get_mut("SAMPLE")
+        .unwrap()
+        .base_point = Vector3::new(10.0, 20.0, 0.0);
+    let reference = app.tabs[i]
+        .scene
+        .document
+        .add_entity(EntityType::Insert(Insert::new(
+            "SAMPLE",
+            Vector3::new(100.0, 200.0, 0.0),
+        )))
+        .unwrap();
+    let _ = app.dispatch_command(&format!("BEDIT_BEGIN:{}", reference.value()));
+    (app, i, reference)
+}
+
+#[test]
+fn block_test_uses_unsaved_definition_and_preserves_editor_history_and_view() {
+    let (mut app, source, _) = fixture();
+    assert_eq!(
+        app.automation_op(r#"{"op":"run","cmd":"CIRCLE 12,20 2"}"#)["ok"],
+        true
+    );
+    app.finish_pending_history(source);
+    let document = app.tabs[source].scene.document.clone();
+    let depth = app.tabs[source].history.undo_stack.len();
+    let camera = app.tabs[source].scene.camera.borrow().clone();
+    let source_id = app.tabs[source].id;
+    assert_eq!(
+        app.automation_op(r#"{"op":"run","cmd":"BTESTBLOCK"}"#)["ok"],
+        true
+    );
+    let test = app.active_tab;
+    assert_ne!(app.tabs[test].id, source_id);
+    assert!(app.tabs[test].active_block_edit.is_none());
+    assert_eq!(
+        app.tabs[test].scene.document.block_records.get("SAMPLE"),
+        document.block_records.get("SAMPLE")
+    );
+    let model = app.tabs[test]
+        .scene
+        .document
+        .header
+        .model_space_block_handle;
+    let top: Vec<_> = app.tabs[test]
+        .scene
+        .document
+        .entities()
+        .filter(|e| {
+            e.common().owner_handle == model
+                && !matches!(e, EntityType::Block(_) | EntityType::BlockEnd(_))
+        })
+        .collect();
+    assert_eq!(top.len(), 1);
+    let EntityType::Insert(reference) = top[0] else {
+        panic!("missing test reference")
+    };
+    assert_eq!(reference.insert_point, Vector3::ZERO);
+    assert_eq!(reference.block_name, "SAMPLE");
+    assert!(app.tabs[test].history.undo_stack.is_empty());
+    assert_eq!(
+        app.automation_op(r#"{"op":"run","cmd":"CIRCLE 1000,1000 8"}"#)["ok"],
+        true
+    );
+    assert_eq!(
+        app.automation_op(r#"{"op":"run","cmd":"BCLOSETESTBLOCK"}"#)["ok"],
+        true
+    );
+    assert_eq!(app.active_tab, source);
+    assert_eq!(app.tabs[source].scene.document, document);
+    assert_eq!(app.tabs[source].history.undo_stack.len(), depth);
+    assert_eq!(app.tabs[source].scene.camera.borrow().target, camera.target);
+    assert!(app.active_modal.is_none());
+    app.undo_steps(1);
+    assert_eq!(
+        app.tabs[source]
+            .scene
+            .document
+            .entities_in_block("SAMPLE")
+            .count(),
+        1
+    );
+}
+
+#[test]
+fn block_test_keytips_follow_context_and_offer_close() {
+    let (mut app, source, _) = fixture();
+    let tab_tip = |app: &OpenCADStudio, target: &str| {
+        app.ribbon.keytips_json(false)["tips"]
+            .as_array()
+            .unwrap()
+            .iter()
+            .any(|tip| tip["target"] == target)
+    };
+    app.ribbon.show_keytips(false);
+    assert!(!tab_tip(&app, "block_test"));
+    let _ = app.ribbon.keytip_type(Some("H"));
+    assert!(tab_tip(&app, "LINE"));
+    assert!(!tab_tip(&app, "BCLOSETESTBLOCK"));
+    let _ = app.ribbon.hide_keytips();
+    let _ = app.open_block_test(source);
+    app.ribbon.show_keytips(false);
+    assert_eq!(app.ribbon.keytips_json(false)["tab"], "draw");
+    assert!(!tab_tip(&app, "block_test"));
+    assert!(!tab_tip(&app, "block_editor"));
+    let _ = app.ribbon.keytip_type(Some("H"));
+    assert!(tab_tip(&app, "LINE"));
+    assert!(tab_tip(&app, "Close"));
+    assert!(tab_tip(&app, "BCLOSETESTBLOCK"));
+    let _ = app.ribbon.keytip_type(Some("C"));
+    let crate::ui::ribbon::KeyTipStep::Run(close) = app.ribbon.keytip_type(Some("T")) else {
+        panic!("close key tip did not dispatch a ribbon action");
+    };
+    assert!(matches!(
+        &close,
+        Message::RibbonToolClick { event: crate::modules::ModuleEvent::Command(command), .. }
+            if command == "BCLOSETESTBLOCK"
+    ));
+    let _ = app.ribbon.hide_keytips();
+    let _ = app.update(close);
+    app.ribbon.show_keytips(false);
+    assert!(!tab_tip(&app, "block_test"));
+    assert!(tab_tip(&app, "block_editor"));
+    assert_eq!(app.ribbon.keytips_json(false)["tab"], "block_editor");
+    let _ = app.ribbon.keytip_type(Some("H"));
+    assert!(!tab_tip(&app, "Close"));
+    assert!(!tab_tip(&app, "BCLOSETESTBLOCK"));
+    let _ = app.ribbon.hide_keytips();
+}
+
+#[test]
+fn block_test_close_x_discards_dirty_edits_and_repeated_test_refreshes() {
+    let (mut app, source, _) = fixture();
+    let _ = app.open_block_test(source);
+    let first = app.tabs[app.active_tab].id;
+    let _ = app.open_block_test(app.active_tab);
+    assert!(!app.tabs.iter().any(|tab| tab.id == first));
+    assert_eq!(
+        app.tabs
+            .iter()
+            .filter(|tab| tab.block_test.is_some())
+            .count(),
+        1
+    );
+    let i = app.active_tab;
+    app.tabs[i].dirty = true;
+    let _ = app.on_tab_close(i);
+    assert_eq!(app.active_tab, source);
+    assert!(app.pending_close.is_none());
+    assert!(app.active_modal.is_none());
+}
+
+#[test]
+fn block_test_refuses_persistence_and_replacing_the_scratch_drawing() {
+    let (mut app, source, _) = fixture();
+    let _ = app.open_block_test(source);
+    let test = app.active_tab;
+    for command in [
+        "SAVE",
+        "QSAVE",
+        "SAVEAS",
+        "SAVEALL",
+        "BSAVE",
+        "BSAVEAS:OTHER",
+        "BEDIT_OPEN:SAMPLE",
+        "REFEDIT",
+    ] {
+        let request = serde_json::json!({"op":"run", "cmd":command});
+        assert_eq!(
+            app.automation_op(&request.to_string())["ok"],
+            false,
+            "{command}"
+        );
+    }
+    assert_eq!(
+        app.automation_op(r#"{"op":"save","path":"blocked-test.dwg"}"#)["ok"],
+        false
+    );
+    assert_eq!(app.automation_op(r#"{"op":"new"}"#)["ok"], false);
+    let _ = app.update(Message::SaveFile);
+    let _ = app.update(Message::SaveAs);
+    assert!(app.active_modal.is_none());
+    assert_eq!(app.active_tab, test);
+    assert!(app.tabs[test].current_path.is_none());
+    assert!(app.active_save_jobs.is_empty());
+    app.tabs[test].dirty = true;
+    let _ = app.update(Message::AutoSave);
+    assert!(app.active_save_jobs.is_empty());
+}
+
+#[test]
+fn block_test_parent_close_cancel_keeps_test_and_discard_removes_it() {
+    let (mut app, source, _) = fixture();
+    app.automation_op(r#"{"op":"run","cmd":"CIRCLE 12,20 2"}"#);
+    let _ = app.open_block_test(source);
+    let test_id = app.tabs[app.active_tab].id;
+    let _ = app.on_tab_close(source);
+    assert_eq!(app.active_modal, Some(ModalKind::BlockEditChanges));
+    let _ = app.update(Message::BlockEditChangesCancel);
+    assert!(app.tabs.iter().any(|tab| tab.id == test_id));
+    let _ = app.on_tab_close(source);
+    let _ = app.update(Message::BlockEditChangesDiscard);
+    assert!(!app.tabs.iter().any(|tab| tab.id == test_id));
+    assert!(!app.tabs.iter().any(|tab| tab.block_test.is_some()));
+}
+
+#[test]
+fn block_test_no_editor_is_refused() {
+    let mut app = OpenCADStudio::new_for_test();
+    app.automation_op(r#"{"op":"new"}"#);
+    let count = app.tabs.len();
+    let _ = app.open_block_test(app.active_tab);
+    assert_eq!(app.tabs.len(), count);
+    assert!(app.command_line.last_error.is_some());
+}
+
+#[test]
+fn block_test_reordering_before_its_source_keeps_close_targets_stable() {
+    let (mut app, source, _) = fixture();
+    let source_id = app.tabs[source].id;
+    let _ = app.open_block_test(source);
+    let test = app.active_tab;
+    app.tabs.swap(source, test);
+    app.active_tab = test;
+    let _ = app.dispatch_command("BEDIT_DISCARD");
+    assert!(!app.tabs.iter().any(|tab| tab.block_test.is_some()));
+    assert_eq!(app.tabs[app.active_tab].id, source_id);
+    assert!(app.tabs[app.active_tab].active_block_edit.is_none());
+    assert_eq!(app.tabs.len(), 1);
+}
+
+#[test]
+fn block_test_unsaved_visibility_states_work_without_changing_the_editor() {
+    let (mut app, source, _) = fixture();
+    let doc = &mut app.tabs[source].scene.document;
+    let owner = doc.block_records.get("SAMPLE").unwrap().handle;
+    let first = doc.block_records.get("SAMPLE").unwrap().entity_handles[0];
+    let mut line = Line::from_points(Vector3::new(10.0, 23.0, 0.0), Vector3::new(15.0, 23.0, 0.0));
+    line.common.owner_handle = owner;
+    let second = doc.add_entity(EntityType::Line(line)).unwrap();
+    let parameter = crate::scene::block_visibility::create(doc, owner, Vector3::ZERO).unwrap();
+    crate::scene::block_visibility::add_state(doc, parameter, "Alternative", 0).unwrap();
+    crate::scene::block_visibility::set_visible(doc, parameter, 0, &[second], false);
+    crate::scene::block_visibility::set_visible(doc, parameter, 1, &[first], false);
+    let original = app.tabs[source].scene.document.clone();
+    let _ = app.open_block_test(source);
+    let test = app.active_tab;
+    let doc = &app.tabs[test].scene.document;
+    let model = doc.header.model_space_block_handle;
+    let reference = doc
+        .entities()
+        .find(|e| e.common().owner_handle == model && matches!(e, EntityType::Insert(_)))
+        .unwrap()
+        .common()
+        .handle;
+    assert!(doc.dynamic_visibility_for_insert(reference).is_some());
+    app.apply_visibility_state(reference, 1);
+    app.finish_pending_history(test);
+    let doc = &app.tabs[test].scene.document;
+    let EntityType::Insert(insert) = doc.get_entity(reference).unwrap() else {
+        unreachable!()
+    };
+    assert_ne!(insert.block_name, "SAMPLE");
+    let visible: Vec<_> = doc
+        .entities_in_block(&insert.block_name)
+        .filter(|e| !e.common().invisible)
+        .collect();
+    assert_eq!(visible.len(), 1);
+    let EntityType::Line(line) = visible[0] else {
+        panic!("expected the alternative line")
+    };
+    assert_eq!(line.start.y, 23.0);
+    assert_eq!(app.tabs[source].scene.document, original);
+    app.visibility_popup = Some(super::visibility::VisibilityPopup {
+        insert_handle: reference,
+        anchor: iced::Point::ORIGIN,
+        items: vec!["Alternative".into()],
+        current: Some(1),
+    });
+    let _ = app.close_block_test(test);
+    assert!(app.visibility_popup.is_none());
+    assert_eq!(app.tabs[source].scene.document, original);
+}
+
+#[test]
+fn block_test_attributes_use_defaults_and_the_stored_base_point() {
+    use codec::entities::AttributeDefinition;
+    let (mut app, source, _) = fixture();
+    let doc = &mut app.tabs[source].scene.document;
+    let owner = doc.block_records.get("SAMPLE").unwrap().handle;
+    let mut attribute = AttributeDefinition::new("TAG".into(), "Value".into(), "default".into());
+    attribute.insertion_point = Vector3::new(12.0, 23.0, 0.0);
+    attribute.common.owner_handle = owner;
+    let definition = doc
+        .add_entity(EntityType::AttributeDefinition(attribute))
+        .unwrap();
+    let _ = app.open_block_test(source);
+    let doc = &app.tabs[app.active_tab].scene.document;
+    let model = doc.header.model_space_block_handle;
+    let insert = doc
+        .entities()
+        .find_map(|entity| match entity {
+            EntityType::Insert(insert) if insert.common.owner_handle == model => Some(insert),
+            _ => None,
+        })
+        .unwrap();
+    assert_eq!(insert.attributes.len(), 1);
+    let attribute = &insert.attributes[0];
+    assert_eq!(attribute.value, "default");
+    assert_eq!(attribute.insertion_point, Vector3::new(2.0, 3.0, 0.0));
+    assert_eq!(attribute.attdef_handle, definition);
+    assert!(!attribute.common.handle.is_null());
+    assert_eq!(attribute.common.owner_handle, insert.common.handle);
+}
+
+#[test]
+fn block_test_close_others_discards_the_test_without_prompting() {
+    let (mut app, source, _) = fixture();
+    let _ = app.open_block_test(source);
+    app.tabs[app.active_tab].dirty = true;
+    let test = app.tabs[app.active_tab].id;
+    let _ = app.update(Message::DocTabCloseOthers(source));
+    assert!(!app.tabs.iter().any(|tab| tab.id == test));
+    assert!(app.active_modal.is_none());
+    assert!(app.tabs[source].active_block_edit.is_some());
+}
diff --git a/src/app/commands/fileops.rs b/src/app/commands/fileops.rs
index b9e6d75a9..825763781 100644
--- a/src/app/commands/fileops.rs
+++ b/src/app/commands/fileops.rs
@@ -38,7 +38,7 @@ impl OpenCADStudio {
                     let mut saved = 0usize;
                     let mut skipped = 0usize;
                     for t in 0..self.tabs.len() {
-                        if self.tabs[t].is_start {
+                        if self.tabs[t].is_start || self.tabs[t].block_test.is_some() {
                             continue;
                         }
                         if let Some(path) = self.tabs[t].current_path.clone() {
diff --git a/src/app/commands/inquiry.rs b/src/app/commands/inquiry.rs
index d5fbd9d9f..43b944a28 100644
--- a/src/app/commands/inquiry.rs
+++ b/src/app/commands/inquiry.rs
@@ -614,6 +614,8 @@ impl OpenCADStudio {
             "BSAVE" => {
                 self.save_block_edit(i);
             }
+            "BTESTBLOCK" => return Some(self.open_block_test(i)),
+            "BCLOSETESTBLOCK" => return Some(self.close_block_test(i)),
             "BSAVEAS" => {
                 self.open_block_save_as_dialog(i);
             }
diff --git a/src/app/commands/mod.rs b/src/app/commands/mod.rs
index 1ea774d8c..467319a6d 100644
--- a/src/app/commands/mod.rs
+++ b/src/app/commands/mod.rs
@@ -149,6 +149,33 @@ impl OpenCADStudio {
         };
         let resolved = self.resolve_alias(cmd);
         let cmd = resolved.as_deref().unwrap_or(cmd);
+        if self.tabs[i].block_test.is_some() {
+            let name = cmd.split([' ', ':']).next().unwrap_or(cmd);
+            if matches!(
+                name,
+                "BEDIT"
+                    | "BEDIT_BEGIN"
+                    | "BEDIT_OPEN"
+                    | "REFEDIT"
+                    | "REFEDIT_BEGIN"
+                    | "BSAVE"
+                    | "BSAVEAS"
+                    | "SAVE"
+                    | "QSAVE"
+                    | "SAVEAS"
+                    | "SAVEALL"
+                    | "WBLOCK"
+                    | "EXPORT"
+                    | "ETRANSMIT"
+                    | "ARCHIVE"
+            ) {
+                self.command_line.push_error(
+                    crate::t!("Close Test Block before saving or opening another block editor.")
+                        .as_ref(),
+                );
+                return Task::none();
+            }
+        }
         if is_spacemouse_command(cmd) {
             return self.run_action(cmd);
         }
diff --git a/src/app/control/actions.rs b/src/app/control/actions.rs
index b87927eca..923f1d775 100644
--- a/src/app/control/actions.rs
+++ b/src/app/control/actions.rs
@@ -410,6 +410,12 @@ impl OpenCADStudio {
     /// this needs no undo snapshot. Format follows the path extension.
     #[cfg(not(target_arch = "wasm32"))]
     pub(super) fn control_wblock(&mut self, req: &Value) -> Result<Task<Message>, Value> {
+        if self.tabs[self.active_tab].block_test.is_some() {
+            return Err(failure(
+                "temporary_document",
+                "Test Block is temporary and cannot be saved",
+            ));
+        }
         let path = string(req, "path")?;
         let document = &self.tabs[self.active_tab].scene.document;
         // A template base keeps its tables/styles in the exported file
diff --git a/src/app/control/mod.rs b/src/app/control/mod.rs
index 1ee429364..caaff5e31 100644
--- a/src/app/control/mod.rs
+++ b/src/app/control/mod.rs
@@ -1148,6 +1148,12 @@ impl OpenCADStudio {
             "view_focus" => self.control_view_focus(req)?,
             #[cfg(not(target_arch = "wasm32"))]
             "save" => {
+                if self.tabs[i].block_test.is_some() {
+                    return Err(failure(
+                        "temporary_document",
+                        "Test Block is temporary and cannot be saved",
+                    ));
+                }
                 let path = req["path"]
                     .as_str()
                     .map(std::path::PathBuf::from)
@@ -1198,6 +1204,12 @@ impl OpenCADStudio {
             // Web: no filesystem path; the drawing comes back in the reply.
             #[cfg(target_arch = "wasm32")]
             "save" => {
+                if self.tabs[i].block_test.is_some() {
+                    return Err(failure(
+                        "temporary_document",
+                        "Test Block is temporary and cannot be saved",
+                    ));
+                }
                 use base64::Engine as _;
                 let default_is_dxf = crate::io::source_is_dxf(None, &self.tabs[i].scene.document);
                 let (version, is_dxf) = super::automation::requested_save_target(
diff --git a/src/app/control/sheets.rs b/src/app/control/sheets.rs
index 42cdb2f2c..aafd39cd8 100644
--- a/src/app/control/sheets.rs
+++ b/src/app/control/sheets.rs
@@ -20,7 +20,10 @@ impl OpenCADStudio {
             self.set_control_result(json!({ "closed": false, "reason": "start_page" }));
             return Ok(Task::none());
         }
-        if self.tabs[index].dirty && !req["discard"].as_bool().unwrap_or(false) {
+        if self.tabs[index].dirty
+            && self.tabs[index].block_test.is_none()
+            && !req["discard"].as_bool().unwrap_or(false)
+        {
             return Err(failure(
                 "document_dirty",
                 "Save the document or pass discard:true",
diff --git a/src/app/document.rs b/src/app/document.rs
index 2fcceaaeb..bc753b254 100644
--- a/src/app/document.rs
+++ b/src/app/document.rs
@@ -207,6 +207,7 @@ pub(super) struct DocumentTab {
     pub(super) history: HistoryState,
     /// Drawing history is suspended while `history` belongs to BEDIT.
     pub(super) block_edit_history: Option<super::block_editor::BlockEditHistory>,
+    pub(super) block_test: Option<super::block_test::BlockTestSession>,
     pub(super) active_layer: String,
     /// Block references whose properties panel shows per-axis Scale X/Y/Z even
     /// though the three factors are currently equal — the user unchecked the
@@ -660,6 +661,7 @@ impl DocumentTab {
             dyn_active: 0,
             history: HistoryState::default(),
             block_edit_history: None,
+            block_test: None,
             active_layer: "0".to_string(),
             props_asym_scale: std::collections::HashSet::new(),
             graph: Default::default(),
diff --git a/src/app/mod.rs b/src/app/mod.rs
index 076f2a07b..3aeeaa516 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -9,6 +9,9 @@ pub(crate) mod config;
 pub use automation::{export_headless, serve};
 mod annotation_data;
 mod block_editor;
+mod block_test;
+#[cfg(test)]
+mod block_test_tests;
 mod block_save_as;
 #[cfg(test)]
 mod block_editor_tests;
diff --git a/src/app/update/command.rs b/src/app/update/command.rs
index 8c476f78d..7ca474523 100644
--- a/src/app/update/command.rs
+++ b/src/app/update/command.rs
@@ -160,7 +160,7 @@ impl OpenCADStudio {
             if self.tabs[idx].is_start {
                 continue;
             }
-            if self.tabs[idx].active_block_edit.is_some() {
+            if self.tabs[idx].active_block_edit.is_some() || self.tabs[idx].block_test.is_some() {
                 tasks.push(self.on_tab_close(idx));
                 if self.pending_block_close.is_some() || self.pending_close.is_some() {
                     break;
@@ -178,6 +178,27 @@ impl OpenCADStudio {
     }
 
     pub(in crate::app) fn on_tab_close(&mut self, idx: usize) -> Task<Message> {
+        let test_return_id = self
+            .tabs
+            .get(idx)
+            .and_then(|tab| tab.block_test.as_ref())
+            .map(|test| {
+                if idx == self.active_tab {
+                    test.source_id
+                } else {
+                    self.tabs[self.active_tab].id
+                }
+            });
+        if test_return_id.is_some() {
+            if idx == self.active_tab {
+                self.cancel_active_grip_edit();
+                self.grip_pending = None;
+                self.visibility_popup = None;
+                self.grip_popup = None;
+                self.grip_hover = None;
+            }
+            self.tabs[idx].dirty = false;
+        }
         // Start tab is fixed — close requests on it are no-ops.
         if self.tabs.get(idx).map_or(false, |t| t.is_start) {
             return Task::none();
@@ -249,6 +270,16 @@ impl OpenCADStudio {
         // The active tab is now either a brand-new blank or a
         // different existing tab; in both cases the ribbon needs
         // to track that doc's defaults / selection. #21.
+        if let Some(index) =
+            test_return_id.and_then(|id| self.tabs.iter().position(|tab| tab.id == id))
+        {
+            self.active_tab = index;
+            self.adopt_header_sysvars(index);
+        }
+        self.ribbon
+            .set_block_testing(self.tabs[self.active_tab].block_test.is_some());
+        self.ribbon
+            .set_block_editing(self.tabs[self.active_tab].active_block_edit.is_some());
         self.sync_ribbon_layers();
         self.sync_ribbon_styles();
         self.sync_ribbon_from_selection();
diff --git a/src/app/update/dialog.rs b/src/app/update/dialog.rs
index 1a33b1db2..7dea3f90b 100644
--- a/src/app/update/dialog.rs
+++ b/src/app/update/dialog.rs
@@ -22,6 +22,9 @@ use iced::{mouse, Point, Task};
 
 impl OpenCADStudio {
     pub(in crate::app) fn open_save_dialog_window(&mut self, tab_idx: usize) -> Task<Message> {
+        if self.refuse_block_test_save(tab_idx) {
+            return Task::none();
+        }
         // Every entry here is Save-As semantics (the SAVEAS command, the
         // recovery save-as, the native failure redirects): the user is
         // choosing a destination, so on the web the FS Access picker must
diff --git a/src/app/update/file.rs b/src/app/update/file.rs
index 94f571b71..5405968bc 100644
--- a/src/app/update/file.rs
+++ b/src/app/update/file.rs
@@ -1759,6 +1759,11 @@ impl OpenCADStudio {
         version: codec::DxfVersion,
         set_current_path: bool,
     ) -> Result<(), crate::io::SaveFailure> {
+        if self.tabs[i].block_test.is_some() {
+            return Err(crate::io::SaveFailure::other(
+                "Test Block is temporary and cannot be saved",
+            ));
+        }
         let previous_autosave = self.autosave_target(i);
         if self.tabs[i].recovery_save_as_required
             && self.tabs[i]
@@ -2423,7 +2428,7 @@ impl OpenCADStudio {
         let mut skipped = 0usize;
         let mut pending: Vec<(crate::app::WebSaveallEntry, codec::CadDocument)> = Vec::new();
         for t in 0..self.tabs.len() {
-            if self.tabs[t].is_start {
+            if self.tabs[t].is_start || self.tabs[t].block_test.is_some() {
                 continue;
             }
             let Some(path) = self.tabs[t].current_path.clone() else {
@@ -3083,6 +3088,9 @@ impl OpenCADStudio {
         set_current_path: bool,
         check_external_change: bool,
     ) -> Task<Message> {
+        if self.refuse_block_test_save(i) {
+            return Task::none();
+        }
         let tab_id = self.tabs[i].id;
         if self
             .pending_native_thumbnail_save
@@ -3751,6 +3759,9 @@ impl OpenCADStudio {
     }
 
     pub(super) fn on_save_file(&mut self) -> Task<Message> {
+        if self.refuse_block_test_save(self.active_tab) {
+            return Task::none();
+        }
         if self.read_only {
             self.command_line.push_error(
                 crate::t!("Read-only session (--read-only): saving is disabled.").as_ref(),
@@ -3807,6 +3818,9 @@ impl OpenCADStudio {
     /// Used by plain Save (QSAVE) on an as-yet-unsaved drawing and by the
     /// save-before-close flow — the version picker is reserved for Save As.
     pub(in crate::app) fn save_with_default_format(&mut self, tab_idx: usize) -> Task<Message> {
+        if self.refuse_block_test_save(tab_idx) {
+            return Task::none();
+        }
         self.active_tab = tab_idx;
         // Every caller of this entry (Save/QSAVE, the save-before-close
         // flow) is plain-save semantics: on the web, the tab's retained
@@ -4199,7 +4213,10 @@ impl OpenCADStudio {
     pub(super) fn on_autosave(&mut self) -> Task<Message> {
         let mut tasks = Vec::new();
         for i in 0..self.tabs.len() {
-            if !self.tabs[i].dirty || self.active_save_jobs.contains_key(&self.tabs[i].id) {
+            if self.tabs[i].block_test.is_some()
+                || !self.tabs[i].dirty
+                || self.active_save_jobs.contains_key(&self.tabs[i].id)
+            {
                 continue;
             }
             self.prepare_snapshot_save(i);
@@ -4234,7 +4251,7 @@ impl OpenCADStudio {
         }
         let mut pending = Vec::new();
         for i in 0..self.tabs.len() {
-            if !self.tabs[i].dirty {
+            if self.tabs[i].block_test.is_some() || !self.tabs[i].dirty {
                 continue;
             }
             // Same pre-serialize state sync the web Save flow performs
@@ -4561,7 +4578,7 @@ impl OpenCADStudio {
         let mut names: Vec<String> = Vec::new();
         let mut active = 0;
         for (index, tab) in self.tabs.iter().enumerate() {
-            if tab.is_start {
+            if tab.is_start || tab.block_test.is_some() {
                 continue;
             }
             if index == self.active_tab {
diff --git a/src/app/update/mod.rs b/src/app/update/mod.rs
index 14443aa96..1817eb818 100644
--- a/src/app/update/mod.rs
+++ b/src/app/update/mod.rs
@@ -346,7 +346,17 @@ impl OpenCADStudio {
             .tabs
             .get(self.active_tab)
             .is_some_and(|tab| tab.active_block_edit.is_some());
-        self.ribbon.set_block_editing(block_editing);
+        let testing = self
+            .tabs
+            .get(self.active_tab)
+            .is_some_and(|tab| tab.block_test.is_some());
+        if testing {
+            self.ribbon.set_block_editing(false);
+            self.ribbon.set_block_testing(true);
+        } else {
+            self.ribbon.set_block_testing(false);
+            self.ribbon.set_block_editing(block_editing);
+        }
         task
     }
 
@@ -595,7 +605,11 @@ impl OpenCADStudio {
             }
         }
         #[cfg(target_arch = "wasm32")]
-        crate::sys::set_unsaved_changes_warning(self.tabs.iter().any(|tab| tab.dirty));
+        crate::sys::set_unsaved_changes_warning(
+            self.tabs
+                .iter()
+                .any(|tab| tab.dirty && tab.block_test.is_none()),
+        );
         if self.tabs[i].active_cmd.is_none() {
             self.block_palette.placing = None;
         }
diff --git a/src/modules/block_editor/mod.rs b/src/modules/block_editor/mod.rs
index 26f0f4379..09b61c71e 100644
--- a/src/modules/block_editor/mod.rs
+++ b/src/modules/block_editor/mod.rs
@@ -63,6 +63,11 @@ impl CadModule for BlockEditorModule {
                             "Close Block Editor",
                             include_bytes!("../../../assets/icons/mt_cancel.svg"),
                         ),
+                        command(
+                            "BTESTBLOCK",
+                            "Test Block",
+                            include_bytes!("../../../assets/icons/edit_block.svg"),
+                        ),
                     ],
                 },
                 RibbonGroup {
diff --git a/src/modules/draw/mod.rs b/src/modules/draw/mod.rs
index 4acb13587..7fb2cc5a7 100644
--- a/src/modules/draw/mod.rs
+++ b/src/modules/draw/mod.rs
@@ -15,7 +15,7 @@ mod report;
 pub mod select;
 pub mod units;
 
-use crate::modules::{CadModule, RibbonGroup, RibbonItem};
+use crate::modules::{CadModule, IconKind, ModuleEvent, RibbonGroup, RibbonItem, ToolDef};
 
 pub struct DrawModule;
 
@@ -249,6 +249,15 @@ impl CadModule for DrawModule {
                         default: "DIST",
                     }],
                 },
+                RibbonGroup {
+                    title: "Close",
+                    tools: vec![RibbonItem::LargeTool(ToolDef {
+                        id: "BCLOSETESTBLOCK",
+                        label: "Close Test Block",
+                        icon: IconKind::Svg(include_bytes!("../../../assets/icons/mt_ok.svg")),
+                        event: ModuleEvent::Command("BCLOSETESTBLOCK".into()),
+                    })],
+                },
                 // Support group lives on the Start tab now (see view.rs:
                 // start_page_view). Removed from the Draw ribbon to declutter.
             ]
diff --git a/src/modules/draw/modify/block_edit.rs b/src/modules/draw/modify/block_edit.rs
index 3d7c0a0d1..0e1720262 100644
--- a/src/modules/draw/modify/block_edit.rs
+++ b/src/modules/draw/modify/block_edit.rs
@@ -119,3 +119,6 @@ inventory::submit!(crate::command::CommandRegistration {
 inventory::submit!(crate::command::CommandRegistration {
     names: &["BSAVE", "BSAVEAS", "BCLOSE"]
 });
+inventory::submit!(crate::command::CommandRegistration {
+    names: &["BTESTBLOCK", "BCLOSETESTBLOCK"]
+});
diff --git a/src/ui/ribbon/keytips.rs b/src/ui/ribbon/keytips.rs
index 906646c18..a7a626eaf 100644
--- a/src/ui/ribbon/keytips.rs
+++ b/src/ui/ribbon/keytips.rs
@@ -434,6 +434,9 @@ const CODES: &[(&str, &str, &str)] = &[
     ("block_editor", "Open and Save", "BO"),
     ("block_editor", "BEDIT", "BE"),
     ("block_editor", "BSAVE", "BS"),
+    ("block_editor", "BTESTBLOCK", "TB"),
+    ("draw", "Close", "TC"),
+    ("draw", "BCLOSETESTBLOCK", "CT"),
     ("block_editor", "ATTDEF", "AD"),
     ("block_editor", "AUTOCONSTRAIN", "AC"),
     ("block_editor", "CCONSTRAINT", "CI"),
@@ -631,7 +634,7 @@ impl Ribbon {
         };
         let scope = module.id();
         let mut tips = Vec::new();
-        for group in module.ribbon_groups() {
+        for group in self.groups_for(index) {
             for item in &group.tools {
                 match item {
                     RibbonItem::Tool(tool)
@@ -709,11 +712,16 @@ impl Ribbon {
     fn item_tips(&self, index: usize, open: &str) -> Vec<Tip> {
         let mut items = draw_panel::keytip_items(open);
         if items.is_empty() {
-            let groups = self.modules.get(index).map(|m| m.ribbon_groups()).unwrap_or(&[]);
-            for item in groups.iter().flat_map(|group| &group.tools) {
-                if let RibbonItem::Dropdown { id, items: list, .. }
-                | RibbonItem::LabeledDropdown { id, items: list, .. }
-                | RibbonItem::LargeDropdown { id, items: list, .. } = item
+            for item in self.groups_for(index).flat_map(|group| &group.tools) {
+                if let RibbonItem::Dropdown {
+                    id, items: list, ..
+                }
+                | RibbonItem::LabeledDropdown {
+                    id, items: list, ..
+                }
+                | RibbonItem::LargeDropdown {
+                    id, items: list, ..
+                } = item
                 {
                     if *id == open {
                         items = list
diff --git a/src/ui/ribbon/locate.rs b/src/ui/ribbon/locate.rs
index e4dd32c35..18c3c3d9a 100644
--- a/src/ui/ribbon/locate.rs
+++ b/src/ui/ribbon/locate.rs
@@ -68,15 +68,11 @@ impl Ribbon {
     fn entries(&self) -> impl Iterator<Item = (usize, Entry<'_>)> {
         let order = std::iter::once(self.active)
             .chain((0..self.modules.len()).filter(move |i| *i != self.active));
-        order
-            .filter_map(|i| self.modules.get(i).map(|m| (i, m)))
-            .flat_map(|(i, module)| {
-                module
-                    .ribbon_groups()
-                    .iter()
-                    .flat_map(group_entries)
-                    .map(move |entry| (i, entry))
-            })
+        order.flat_map(|i| {
+            self.groups_for(i)
+                .flat_map(group_entries)
+                .map(move |entry| (i, entry))
+        })
     }
 
     /// The button id that runs the command line `cmd`: an exact match first,
@@ -111,12 +107,7 @@ impl Ribbon {
     /// module has no tab (its tools are on the side toolbar).
     pub(super) fn tab_holding_active_tool(&self) -> Option<usize> {
         let id = self.active_tool.as_deref()?;
-        let holds = |i: usize| {
-            self.modules[i]
-                .ribbon_groups()
-                .iter()
-                .any(|group| group_holds(group, id))
-        };
+        let holds = |i: usize| self.groups_for(i).any(|group| group_holds(group, id));
         if self
             .modules
             .get(self.active)
diff --git a/src/ui/ribbon/mod.rs b/src/ui/ribbon/mod.rs
index 86680973b..bae9d8b1a 100644
--- a/src/ui/ribbon/mod.rs
+++ b/src/ui/ribbon/mod.rs
@@ -126,6 +126,7 @@ pub struct Ribbon {
     /// A block editor session is open: the tab that was active before the
     /// Block Editor tab took over.
     block_editing: Option<usize>,
+    block_testing: Option<usize>,
     /// XDWGFADECTL as the Reference slide-out shows it (negative = off).
     pub xref_fade: i32,
     /// Open key tips (Alt).
@@ -231,6 +232,7 @@ impl Ribbon {
             xref_ctx: false,
             point_cloud_ctx: None,
             block_editing: None,
+            block_testing: None,
             xref_fade: 50,
             keytips: None,
         }
@@ -328,6 +330,40 @@ impl Ribbon {
         }
     }
 
+    pub fn set_block_testing(&mut self, testing: bool) {
+        if testing != self.block_testing.is_some() {
+            self.close_dropdown();
+            let _ = self.hide_keytips();
+        }
+        let Some(index) = self.modules.iter().position(|module| module.id() == "draw") else {
+            return;
+        };
+        match (testing, self.block_testing) {
+            (true, None) => {
+                self.block_testing = Some(self.active);
+                self.active = index;
+            }
+            (false, Some(previous)) => {
+                self.block_testing = None;
+                if self.active == index {
+                    self.active = previous.min(self.modules.len().saturating_sub(1));
+                }
+            }
+            _ => {}
+        }
+    }
+
+    /// Contextual panels share their normal tab with the drawing tools.
+    fn groups_for(&self, index: usize) -> impl Iterator<Item = &RibbonGroup> {
+        let testing = self.block_testing.is_some();
+        self.modules.get(index).into_iter().flat_map(move |module| {
+            module
+                .ribbon_groups()
+                .iter()
+                .filter(move |group| module.id() != "draw" || group.title != "Close" || testing)
+        })
+    }
+
     pub fn select(&mut self, index: usize) {
         if index < self.modules.len() {
             self.active = index;
@@ -733,38 +769,36 @@ impl Ribbon {
         } else {
             self.active
         };
-        let tool_area: Element<'_, Message> =
-            if let Some(module) = self.modules.get(effective_active) {
-                let groups = module.ribbon_groups();
-                let style_ctx = StyleContext {
-                    text_style_names: &self.text_style_names,
-                    active_text_style: &self.active_text_style,
-                    dim_style_names: &self.dim_style_names,
-                    active_dim_style: &self.active_dim_style,
-                    mleader_style_names: &self.mleader_style_names,
-                    active_mleader_style: &self.active_mleader_style,
-                    table_style_names: &self.table_style_names,
-                    active_table_style: &self.active_table_style,
-                };
-
-                // Adaptive tool area: panels sit on one row; when they don't all
-                // fit they degrade from the right — a panel's large buttons first
-                // shrink to compact icon columns, then it collapses to a ▾ flyout
-                // button. See `CollapsePanels`.
-                let ts = self.toggle_state(show_block_palette);
-                let panels: Vec<Panel<'_>> = groups
-                    .iter()
-                    .map(|g| self.panel(g, ts, &style_ctx, &|_| Vec::new()))
-                    .collect();
-                CollapsePanels::new(panels, self.collapsed_open.clone(), TOOL_BAR_H)
-                    .report_height(self.tool_bar_h.clone())
-                    .report_tight(self.collapse_tight.clone())
-                    .mode(self.collapse_mode)
-                    .into()
-            } else {
-                text("").into()
+        let tool_area: Element<'_, Message> = if self.modules.get(effective_active).is_some() {
+            let groups = self.groups_for(effective_active);
+            let style_ctx = StyleContext {
+                text_style_names: &self.text_style_names,
+                active_text_style: &self.active_text_style,
+                dim_style_names: &self.dim_style_names,
+                active_dim_style: &self.active_dim_style,
+                mleader_style_names: &self.mleader_style_names,
+                active_mleader_style: &self.active_mleader_style,
+                table_style_names: &self.table_style_names,
+                active_table_style: &self.active_table_style,
             };
 
+            // Adaptive tool area: panels sit on one row; when they don't all
+            // fit they degrade from the right — a panel's large buttons first
+            // shrink to compact icon columns, then it collapses to a ▾ flyout
+            // button. See `CollapsePanels`.
+            let ts = self.toggle_state(show_block_palette);
+            let panels: Vec<Panel<'_>> = groups
+                .map(|g| self.panel(g, ts, &style_ctx, &|_| Vec::new()))
+                .collect();
+            CollapsePanels::new(panels, self.collapsed_open.clone(), TOOL_BAR_H)
+                .report_height(self.tool_bar_h.clone())
+                .report_tight(self.collapse_tight.clone())
+                .mode(self.collapse_mode)
+                .into()
+        } else {
+            text("").into()
+        };
+
         let tool_bar: Element<'_, Message> = container(tool_area)
             .style(|theme: &Theme| container::Style {
                 background: Some(Background::Color(theme.palette().background.weakest.color)),
@@ -931,8 +965,7 @@ impl Ribbon {
             return Some(ov);
         }
 
-        let module = self.modules.get(self.active)?;
-        let groups = module.ribbon_groups();
+        let groups = self.groups_for(self.active);
         let mut items_list: Option<Vec<(&'static str, &'static str, IconKind)>> = None;
         let mut dd_default = "";
         let mut dd_id: &'static str = "";
@@ -1161,7 +1194,7 @@ impl Ribbon {
     /// Draw-tab dropdowns — so the list grows to fit its entries instead of
     /// being clipped to the ribbon-row height. (#153)
     fn style_combo_overlay(&self, open_id: &str, win: (f32, f32)) -> Option<Element<'_, Message>> {
-        let groups = self.modules.get(self.active)?.ribbon_groups();
+        let groups = self.groups_for(self.active);
 
         // Locate the open style combo; capture its style key + manager command.
         let mut found: Option<(crate::modules::StyleKey, Option<&'static str>)> = None;
@@ -1677,6 +1710,41 @@ mod tests {
     use super::widgets::is_active_tool;
     use super::Ribbon;
 
+    #[test]
+    fn block_test_close_panel_extends_draw_only_while_testing() {
+        let mut ribbon = Ribbon::default();
+        let draw = ribbon
+            .modules
+            .iter()
+            .position(|module| module.id() == "draw")
+            .unwrap();
+        assert!(!ribbon
+            .modules
+            .iter()
+            .any(|module| module.id() == "block_test"));
+        let ordinary: Vec<_> = ribbon.groups_for(draw).map(|group| group.title).collect();
+        assert!(!ordinary.contains(&"Close"));
+        ribbon.set_block_editing(true);
+        ribbon.set_block_editing(false);
+        ribbon.set_block_testing(true);
+        assert_eq!(ribbon.active, draw);
+        let testing: Vec<_> = ribbon.groups_for(draw).map(|group| group.title).collect();
+        assert_eq!(&testing[..ordinary.len()], ordinary.as_slice());
+        assert_eq!(testing.last(), Some(&"Close"));
+        ribbon.toggle_collapsed_panel("Close");
+        ribbon.set_block_testing(false);
+        assert!(ribbon.collapsed_open.is_none());
+        assert_eq!(
+            ribbon
+                .groups_for(draw)
+                .map(|group| group.title)
+                .collect::<Vec<_>>(),
+            ordinary
+        );
+        ribbon.set_block_editing(true);
+        assert_eq!(ribbon.modules[ribbon.active].id(), "block_editor");
+    }
+
     #[test]
     fn block_palette_highlight_follows_the_app_state_passed_to_the_view() {
         // The Block Palette button highlight is derived from the app's